In the field of electric arc furnaces for use in the iron and steel industry, it is known to make openings on the side walls of the furnace chamber (or shaft). Devices (or injectors) such as auxiliary burners and/or lances can be inserted through these openings.
Particularly, it is known to use auxiliary burners that allow adding further amounts of heat to the heat provided by the electric arc in order to facilitate and accelerate metal bulk melting. It is also known to use dispensers that are capable of simultaneously injecting gases and powders into the shaft. By “lance” is normally meant a supersonic gas dispenser or a high-speed powder dispenser. Dispensers and lances, besides functioning as gas injectors or burners, allow introducing additives in the molten metal bath, which are used during the metallurgical process, such as coal, lime or powders.
Auxiliary burners, dispensers and lances will be referred to herein below as “injectors”.
These injectors, in order to obtain maximum effectiveness, must be placed as deep within the furnace as possible, proximate to the molten bath. In this configuration, they are intended to operate at the furnace operating temperature, i.e. about 1500° C.-1700° C., and are further exposed to possible splashes of liquid steel and slag. These are very hard operating conditions, which cause the injector to be very rapidly worn.
Considerable wear levels of the injector can cause a water leakage from the cooling circuit within the furnace, with a consequent worsening in the operating conditions. Furthermore, any water infiltration below the layer of refractory material may cause the formation of vapour that results in a rapid volume and pressure increase having the effect of an actual explosion.
A water leakage at the furnace operating temperatures further involves a risk related to the cleavage of water into hydrogen and oxygen. This means a further risk of explosion.
Furthermore, the injector wear involves the risk that leakage may occur in the circuits of the fuel and/or oxidizer that are delivered into the furnace by the injector. In this case, fuel and oxidizer would no longer come to be admixed in the area arranged for combustion within the furnace, but would admix upstream of the injector thus causing, again, a serious risk of explosion.
From what has been stated above, it is thus understood how a ready replacement of the worn injector is important. As known injectors are composed by a structure made of steel and copper welded to each other, those skilled in the art will appreciate how a frequent replacement of the injectors negatively affects the operating costs of a furnace.